This possibility intrigued two researchers—Amar Cheema of the University of Virginia and Vanessa M. Patrick of the University of Houston—so they carried out an innovative study of real-world behavior: they gathered sales data for various types of lottery games in St. Louis County for a full year, then looked for differences in sales patterns as a function of each day’s temperature. The results were striking. Sales for scratch tickets, which require buyers to choose between many different options, fell by $594 with every 1° Fahrenheit increase in temperature. Sales for lotto tickets, which require fewer decisions on the part of the buyer, were not affected.
The researchers decided to test this apparent link between weather and complex decision-making in the lab by performing a series of experiments comparing participants’ cognitive performance at two seemingly unremarkable temperatures: 67° and 77° Fahrenheit. People tend to be most comfortable at around 72° Fahrenheit, so each temperature represented just a 5° deviation from maximum comfort.
Despite this minimal deviation in temperature, the researchers found remarkable differences in cognitive functioning. In one lab study, participants were asked to proofread an article while they were in either a warm (77°) or a cool (67°) room. Participants in warm rooms performed significantly worse than those in cool rooms, failing to identify almost half of the spelling and grammatical errors (those in cool rooms, on the hand, only missed a quarter of the mistakes). These results suggest that even simple cognitive tasks can be adversely affected by excessive ambient warmth.
In a second study, the researchers showed similar effects for more complex cognitive calculations. In this study, another group of participants were asked to choose between two cell phone plans, again in either a warm or a cool room. One plan looked more attractive on the surface, but was actually more expensive; simple patterns of decision-making would therefore lead participants to choose the more expensive plan, whereas more complex analyses would lead participants to correctly choose the more cost-effective plan. Participants in the cool room made the correct choice over half the time; those in the warm room, on the other hand, made the correct choice only a quarter of the time. Warmer temperatures seemed to make participants more likely to rely on simplistic patterns of decision-making, which in turn led to inferior choices. These results suggest that complex decision-making, like simple cognitive tasks, is adversely affected by warm temperatures.
A third study suggests that warm surroundings may not just cause people to fail at complex decision-making—it may cause them to shy away from making these sorts of decisions in the first place. In this study, participants were placed in either a warm or a cool room and asked to choose between two products: an innovative one and a traditional one. Participants in warm rooms, relative to those in cool rooms, were much more likely to choose the traditional product—ostensibly because they did not have the cognitive resources necessary to evaluate the new information relevant to an innovative item.
Of course, demonstrating temperature-related differences in cognitive functioning does not necessarily mean that these differences are due to depleted glucose supplies. Nor does it rule out the possibility that these effects are driven by improvements in cognitive ability under cooler conditions (as opposed to impairment under warmer conditions). With these alternate interpretations in mind, the researchers added one crucial component to each study: they depleted glucose supplies for half of the participants before placing them into warm or cool rooms, and left the other half undepleted. Participants in warm conditions behaved almost exactly like pre-depleted participants; this suggests that warm temperatures result in natural resource depletion, which in turn impairs cognitive functioning.